Esophagus to Small Intestine
BMJ. 2024;384:e077310
Ultra-processed food exposure and adverse health outcomes: Umbrella review of epidemiological meta-analyses
Objective: To evaluate the existing meta-analytic evidence of associations between exposure to ultra-processed food (UPF), as defined by the Nova food classification system, and adverse health outcomes.
Design: Systematic umbrella review of existing meta-analyses. Data sources: Medline, PsycINFO, Embase, and the Cochrane Database of Systematic Reviews, as well as manual searches of reference lists from 2009 to June 2023. Eligibility criteria for selecting studies: Systematic reviews and meta-analyses of cohort, case-control, and/or cross-sectional study designs. To evaluate the credibility of evidence, pre-specified evidence classification criteria were applied, graded as convincing (“class I”), highly suggestive (“class II”), suggestive (“class III”), weak (“class IV”), or no evidence (“class V”). The quality of evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development, and Evaluations) framework, categorised as “high,” “moderate,” “low,” or “very low” quality.
Results: The search identified 45 unique pooled analyses, including 13 dose-response associations and 32 non-dose-response associations (n = 9,888,373). Overall, direct associations were found between exposure to UPF and 32 (71%) health parameters spanning mortality, cancer, and mental, respiratory, cardiovascular, gastrointestinal, and metabolic health outcomes. Based on the pre-specified evidence classification criteria, convincing evidence (class I) supported direct associations between greater UPF exposure and higher risks of incident cardiovascular disease related mortality (risk ratio [RR] = 1.50, 95% confidence interval: 1.37–1.63; GRADE = very low) and type 2 diabetes (dose-response RR = 1.12, 1.11–1.13; moderate), as well as higher risks of prevalent anxiety outcomes (odds ratio [OR] = 1.48, 1.37–1.59; low) and combined common mental disorder outcomes (OR = 1.53, 1.43–1.63; low). Highly suggestive (class II) evidence indicated that greater exposure to UPF was directly associated with higher risks of incident all-cause mortality (RR = 1.21, 1.15–1.27; low), heart disease-related mortality (hazard ratio [HR] = 1.66, 1.51–1.84; low), type 2 diabetes (OR = 1.40, 1.23–1.59; very low), and depressive outcomes (HR = 1.22, 1.16–1.28; low), together with higher risks of prevalent adverse sleep-related outcomes (OR = 1.41, 1.24–1.61; low), wheezing (RR = 1.40, 1.27–1.55; low), and obesity (OR = 1.55, 1.36–1.77; low). Of the remaining 34 pooled analyses, 21 were graded as suggestive or weak strength (class III–IV) and 13 were graded as no evidence (class V). Overall, using the GRADE framework, 22 pooled analyses were rated as low quality, with 19 rated as very low quality and 4 rated as moderate quality.
Conclusions: Greater exposure to ultra-processed food (UPF) was associated with a higher risk of adverse health outcomes, especially cardiometabolic, common mental disorder, and mortality outcomes. These findings provide a rationale to develop and evaluate the effectiveness of using population-based and public health measures to target and reduce dietary exposure to UPF for improved human health. They also inform and provide support for urgent mechanistic research.